Michitaka Sakai is a second‑year student at Tokise High School and a member of the school’s koto club. He is known among his friends by the nickname Mittsu, a shortened, familiar form of his name. Before joining the club, Sakai had a reputation as a delinquent and was often involved in fights around school, but he never enjoyed the violence and was always the most level‑headed member of his group. He dislikes being judged by appearances, a sentiment shaped by his own experience of being stereotyped as a troublemaker.

Sakai’s primary motivation for joining the koto club was to support his close friend Chika Kudo in fulfilling the dream of honoring Chika’s grandfather. He had no previous musical training but developed his skills through dedicated practice, quickly becoming a capable player. His analytical nature allows him to break down complex koto pieces and notice timing issues that even more experienced members sometimes overlook. His calm demeanor frequently helps de‑escalate disputes within the club, especially during tense exchanges between Chika and rivals from other schools.

Within the story, Sakai acts as a stabilizing presence in the club. He values the moments when the ensemble’s sound blends perfectly, describing it as everyone’s sound coming together. His loyalty extends beyond musical activities; he once confronted bullies who were bad‑mouthing fellow club member Sane Osaka. Over the course of the series, Sakai grows from a supportive outsider into a fully committed member of the koto club, contributing not only his steady personality but also a sharp ear for detail that strengthens the group’s performances. His ability to remain composed under pressure and his willingness to back his friends make him an integral part of the club’s revival and success.